Add an example for using the reflection API (#5839)

* Add an example for using the reflection API

The example program is meant to accompany a document that goes into more detail about the mental model behind the reflection API and the way this program drives it.
Ideally this program can land before the document goes live, and then the document can be published with a link to the example.
After that, the example could be updated to include links into the live document.

Along with adding the example program, this change also adds some convenience functions to the reflection API to avoid cases where the program would otherwise need to cast between
`slang::ParameterCategory` and `SlangParameterCategory`.

* format code

* fixup: error noticed by clang

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

examples/CMakeLists.txt

@@ -83,6 +83,7 @@ if(SLANG_ENABLE_EXAMPLES)
     example(platform-test WIN32_EXECUTABLE)
     example(ray-tracing WIN32_EXECUTABLE)
     example(ray-tracing-pipeline WIN32_EXECUTABLE)
+    example(reflection-api)
     example(shader-object)
     example(shader-toy WIN32_EXECUTABLE)
     example(triangle WIN32_EXECUTABLE)

examples/reflection-api/README.md

@@ -0,0 +1,6 @@
+Slang Reflection API Example
+============================
+
+This example shows basic usage of the Slang reflection API to
+traverse the parameters of a program, including type and
+layout information.

examples/reflection-api/compute-simple.slang

@@ -0,0 +1,21 @@
+// compute-simple.slang
+
+struct ImageProcessingOptions
+{
+    float3 tintColor;
+    float blurRadius;
+
+    bool useLookupTable;
+    StructuredBuffer<float4> lookupTable;
+}
+
+[shader("compute")]
+[numthreads(8, 8)]
+void processImage(
+    uint3 threadID : SV_DispatchThreadID,
+    uniform Texture2D inputImage,
+    uniform RWTexture2D outputImage,
+    uniform ImageProcessingOptions options)
+{
+    /* actual logic would go here */
+}